Liquid crystal displays have become increasingly popular in recent years owing to their advantages such as low operating voltage, low power consumption and radiation, light weight and thin design.
With the improvement of living standards, increasingly high standards are required for display performance including high brightness, high contrast and high response speed. Standards for the image quality of the entire display are also increasingly high, such as mura and image sticking, wherein mura refers to the phenomenon of a variety of traces resulting from uneven brightness of the display; image sticking, also named as image persistence, refers to the phenomenon of afterimage when the same still picture has been displayed for a long time and then the display content is changed.
Image sticking affects image quality seriously. In the prior art, the problem of image sticking is generally solved by the following two methods. The first method tries to reduce the occurrence chance of image sticking by changing the design of thin film transistor (TFT). But the design change often alters the previous design scheme only after image sticking appears, and thus changing the design of the thin film transistor takes efforts almost close to developing a new product, and there is no guarantee that the image problem will be improved. Moreover, the TFT design change will make the cycle of the product development longer and double the development cost. The second method tries to reduce the occurrence chance of image sticking by changing the alignment film material and its manufacturing process. However, change of the manufacturing process generally refers to change of the thickness of the metal film layer (the metal film layer may include a Mo/Al layer), the thickness of the alignment film and the thickness of the transparent over coat (OC), so as to delay the release time of ion impurities. But change of the alignment film material and its manufacturing process can only delay the time when the image sticking appears, and cannot actually make the image sticking disappear. Therefore, the two methods can not fundamentally solve the problem of image sticking.